The present invention relates to an industrial robot and, particularly, to such a robot which is capable of accurately fitting an assembling member into a corresponding hole formed in an assembling base fixedly secured to a support structure to implement an assembly operation.
FIG. 1 is a front view of a hand of a conventional industrial robot for fitting a part to a base, in which an automatic alignment device 6 is composed of a upper plate 6a fixedly secured to a rotary shaft 5 extending vertically from a free end of a robot arm 4, a core member 6b extending vertically from the upper plate 6a, a lower plate 6c arranged in parallel to the upper plate 6a, and a link mechanism for movably supporting the lower plate 6c in parallel to the upper plate 6a. The link mechanism is composed of three parallel links each having, at opposite ends thereof, spheres which are received in spherical bearings 6d' and 6d"' provided correspondingly on a lower surface of the upper plate 6a and an upper surface of the lower plate 6c.
A cylinder member 6e is fixed to the lower plate 6c. Its length is sufficient to extend over a lower portion of the core member 6b.
Such lower portion of the core member 6b is supported by an elastic member 6f within the cylinder member 6e to allow a relative movement therebetween. A gripper 7 is mounted on the lower plate 6c and has gripping nails 7a actuated by an air or oil pressure motor to grip a workpiece 8 in the form of a rod member having a chamfered end 8a which is to be inserted into a blind hole 10a formed in a workpiece 10 disposed fixedly on a table 9. The hole has a chamfered opening 10b.
When an elevation shaft of the robot is lowered to fit the rod member 8 into the hole 10a with a center axis of the rod member 8 deviating slightly from a center axis of the hole 10a, the fitting can be achieved as long as the mount of deviation is within the range of the chamfer 8a of the rod member 8, due to the deformation of the elastic member 6f as shown in FIG. 2. Therefore, under these conditions, by lowering the elevation shaft, the rod member 8 can be inserted automatically into the hole 10a and the desired assembling operation is achieved.
In the conventional hand device mentioned above, the manufacturing cost is high due to such complicated mechanical structure, and the size of the hand cannot be reduced, resulting in a lowered space efficiency.